This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. X-linked retinoschisis (XLRS) is an inherited form of retinal degeneration affecting young males. It is caused by mutations in a gene (retinoschisin or RS1) that is required for normal retinal function. Patients present with poor vision in infancy or at school age. Visual acuity usually worsens during the teenage years and then stabilizes until complicated by vitreous hemorrhage or retinal detachment during adulthood. In a previous study in a rodent animal model of XLRS, treatment with an AAV-RS1 gene therapy vector resulted in progressive and long-term improvement in retinal function and prevention of retinal cell degeneration. This project is testing the safety and biodistribution of AAV-RS1 vector injected subretinally in nonhuman primates, as a critical final step prior to a planned human clinical trial of this potentially sight-saving new therapy.